Mechanism and Characteristics of Phosphorus Release from Sediments in Drawdown Zone Under Inundation/Drying Cycles

Area of Science:

• Environmental Science
• Limnology
• Ecosystem Dynamics

Background:

• Sediment phosphorus release is a major driver of eutrophication in shallow lakes.
• Drawdown zone dynamics under fluctuating water levels are understudied, impacting water quality management.

Purpose of the Study:

• To investigate the mechanisms of phosphorus release from sediments in the drawdown zone of Nansi Lake.
• To analyze the influence of inundation duration, physicochemical properties, and organic matter decomposition on phosphorus release.

Main Methods:

• Field sampling and laboratory simulations were employed to study phosphorus release.
• Analysis included monitoring phosphorus concentrations in overlying and interstitial water.
• Physicochemical parameters (pH, ORP, DO, TOC) and inundation duration were assessed.

Main Results:

• Significant phosphorus release occurred during inundation, with higher concentrations observed during the second inundation period.
• Inorganic phosphorus, particularly dissolved inorganic phosphorus (DIP), dominated the released phosphorus.
• Physicochemical factors (pH, ORP, DO) and organic matter decomposition influenced phosphorus distribution and release rates.

Conclusions:

• Drawdown zone sediments are a critical internal phosphorus source in shallow lakes like Nansi Lake.
• Integrated management strategies are needed to control internal phosphorus loading and prevent eutrophication.
• Findings offer guidance for water quality management in similar lake systems.